ASTM C448:88(R2021) pdf free download – Standard Test Methods for Abrasion Resistance of Porcelain Enamels.
7. Reference Standards
7.1 Specimens of standard calibrated plate glass6 which shows a coefficient of variation no greater than I .5 % when tested for surface abrasion in accordance with the procedure as specified in Section 10, and which meets requirements of Table A 1.4 shall be used as reference standards.
8. Test Specimens
8.1 Test specimens shall be 4/ ± ¼ in. (111.1 ± 6.4 mm) square, and may be prepared by enameling metal blanks of that size or by cutting a larger piece. Specimens for the weight loss tests should not exceed the capacity of the analytical balance selected for obtaining the weights of the specimens. When gloss measurements are to be made, the specimens tested should be as flat and free of orange peel or wavy surface as possible. Variations from flatness decrease the accuracy of gloss measurements.
8.2 Six specimens shall be tested for each determination of resistance to surface abrasion or resistance to subsurface abrasion.
9. Specimen Preparation
9.1 Before making any measurements, wash each specimen with a soft sponge moistened with a warm 1 % solution of trisodium phosphate (distilled water not essential) and rinse in warm, running tap water. If, when rinsing, the water gathers in drops on the surface, repeat the washing treatment until the rinse water spreads evenly. While the specimen is still wet, rinse it with ethyl alcohol. A small stream of alcohol from an ordinary chemical wash bottle will suffice for rinsing. Pure ethyl alcohol is preferable, hut if it is not available, ethyl alcohol that has been denatured with up to 5 % of a noncorrosive, highly volatile organic compound such as methyl alcohol may be used. Allow the specimens to air dry in a vertical position and then place in a desiccator. This will prevent damage and moisture absorption of the specimens which can adversely affect the weight values. Gloss and weight determinations should be obtained within a I 5—mm period after the specimens have been cleaned and placed in the desiccator.
NOTE 2—Other denaturants. approved by the U. S. Bureau of internal Revenue, that are not objectionable for this use are ethyl ether and bcnzcne, either alone or in combination with methyl alcohol. If ethyl alcohol is not available, isopropyl alcohol or acetone may be used, but pure ethyl alcohol is recommended if available. Avoid alcohol denatured with an ingredient of low volatility, which will remain as a surface film on the specimen when used to rinse it before or after treatment. Surface films may significantly affect gloss readings.
10. Resistance to Surface Abrasion of Porcelain Enamels Having 45° Specular Gloss of More than 30 Gloss
Units
10. 1 Marking of Speciniens (111(1 Determining Inhti(1l 45° Specular Gloss—Mark each specimen so that its orientation may be controlled. A mark on the back at one edge will suffice.